1. Field of the Invention
This invention relates to axle assemblies of the kind comprising a housing in which is disposed a crown wheel and pinion gearing providing for drive from an input element connected to the pinion to an output element or elements connected directly or by way of a differential gearing to the crown wheel, the input element and pinion being supported by bearings carried in a part of the housing. Such an assembly will hereafter be referred to as an assembly of the kind specified. The invention has been developed in relation to assemblies of the kind specified wherein the crown wheel and pinion gearing is of the hypoid type, in which the axis of rotation of the pinion is offset from the axis of rotation of the crown wheel, but it is also applicable to assemblies of the spiral bevel type in which the rotational axes of the crown wheel and pinion intersect.
Satisfactory service of an axle assembly of the kind specified is dependent on, among other factors, the maintenance of an adequate supply of lubricant to the bearings which support the input element connected to the pinion. It is usual to provide a quantity of liquid lubricant within the housing of the assembly, and supply of such lubricant to the bearings must then be provided for. In the case of an assembly utilising hypoid gearing, in an installation in which the axis of rotation of the pinion is beneath the axis of rotation of the crown wheel, it is relatively easy to arrange for lubricant to be delivered to the bearings. This is facilitated by the static lubricant level within the housing generally being somewhere approaching the position of the bearings.
If, however, the same assembly should be used in an orientation in which the axis of rotation of the input element is above that of the crown wheel, e.g. if the assembly were used in a vehicle in which maximum ground clearance is desired, it is more difficult to ensure adequate lubrication of the input element and pinion bearings. If the assembly is required to operate at low speeds only, the problem can be overcome by increasing the static level of lubricant within the housing, but this expedient leads to excessive losses due to churning of lubricant if run at high speeds.
2. Summary of Prior Art
It has been proposed, in British Pat. No. 1,188,863, to provide for lubrication of the input element and pinion bearings by lubricant carried by and thrown from the periphery of the crown wheel due to rotation thereof. By appropriate arrangement of lubricant trapping passages or formations, lubrication can be provided for either orientation of the installed assembly. However, if the vehicle in which the axle is installed is travelling slowly, carrying of lubricant by the pinion and the throwing off of the lubricant therefrom does not occur, and inadequate lubrication can result. There have been many other proposals for lubrication of differential gearing associated with crown wheels in axles in various circumstances, and examples are disclosed typically in British Pat. Nos. 590,867; 1,482,116; 1,448,079; but none is concerned with pinion bearing lubrication, and proposals involving "scraping" of lubricant from a rotating surface by an element which contacts the surface; e.g. British Pat. Nos. 1,172,952 and 1,124,697; we regard as unsatisfactory.